The child's body was found in a wooded Washington Heights area in 1991

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The suspect in the back of a police car, on his way to court Saturday. At inset, a police sketch of the little girl known as Baby Hope from one of her missing flyers.

Police say they have solved the 22-year-old mystery of "Baby Hope," the child whose body was found dumped in a cooler in the woods in upper Manhattan in 1991, announcing the arrest Saturday of a cousin they say sexually assaulted and smothered the 4-year-old girl.

Police Commissioner Ray Kelly said 52-year-old Conrado Juarez was visiting relatives, staying at his sister's house in Queens, when he attacked the girl, whose real name is Anjelica Castillo.

Juarez allegedly told police on Friday that when Anjelica went motionless, he summoned his sister into the room, and she ordered him to get rid of the body, bringing him the cooler. The pair then took a livery cab to Manhattan from the sister's Queens home, and dumped the cooler, he said.

It was not clear if he had a lawyer. Kelly said Juarez's sister is no longer alive.

The girl's body was found by construction workers on July 23, 1991 along the Henry Hudson Parkway near Dyckman Street.

Her identity was not known until this week. Detectives in the cold case had even paid for her headstone, inscribing it with the message "Because We Care," Kelly said.

Manhattan District Attorney Cyrus Vance Jr. said in a statement Saturday that investigators never gave up.

"They made it their mission to identify this young child, to lay her to rest and to bring her killer to justice," he said.

Investigators launched a renewed push this summer for leads in the case, and it was amid that publicity for "Baby Hope" that a tipster contacted police, saying she thought she might know the child's sister, now an adult.

That tip led detectives to relatives of the girl, and eventually her mother. This week, the child's real name was finally learned.

Police said Anjelica was staying with Juarez's sister because her parents had recently split up.

A law enforcement official tells NBC 4 New York that the mother claims she lived in fear of the baby's father and was afraid to go to police after her daughter disappeared.